Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$162.58	3.557%	$168.363	$168.36	$168.35	$168.40
Purchase #2	$142.88	13.627%	$162.3503	$162.35	$162.35	$162.40
Purchase #3	$142.64	6.738%	$152.2511	$152.25	$152.25	$152.30
Purchase #4	$89.44	9.600%	$98.0262	$98.03	$98.05	$98.00
Purchase #5	$31.85	3.733%	$33.039	$33.04	$33.05	$33.00
Purchase #6	$48.57	4.714%	$50.8596	$50.86	$50.85	$50.90
Purchase #7	$20.59	9.727%	$22.5928	$22.59	$22.60	$22.60
7 purchase totals =	$638.55		$687.4820	$687.48	$687.50	$687.60